Talk to Gynecologist on Cramps

I'm an 18 year's old girl..who faces severe menstrual cramps on the onset of my cycle. The pain continues for 3 to 4 days.. it's horrible on the onset for 5 to 6 hours that I can't function properly, actually can't even walk and have to vomit once or twice usually. Then on my second and third day it gets better..but still I can't continue with my work for long as it starts hurting me.